Police investigating the disappearance of British girl Madeleine McCann have begun searching an area of scrubland near the holiday apartment in Portugal where she vanished seven years ago.

The area in Praia da Luz on the Algarve was cordoned off and police officers were seen in the area with sniffer dogs.

It is believed the area has been searched before.

The joint Portuguese-British operation could last up to a week, and take in three different patches of land, according to Portuguese media reports.

British detectives said last month they had received authorisation from the Portuguese authorities to search near the resort complex where Madeleine disappeared from her bedroom in May 2007 as her parents dined with friends at a nearby tapas restaurant.

Scotland Yard, which is carrying out its own investigation, refused to comment on reports that British officers were at the scene and said the force was "not prepared to give a running commentary" on the case.

Two weeks ago, Metropolitan Police assistant commissioner Mark Rowley said detectives were examining every credible line of inquiry in the search for Madeleine, who was almost four when she disappeared.

He said: "In the forthcoming weeks we are going to be going to a substantial phase of operational activity on the ground in Portugal.

"It's something that you would expect in any major inquiry.

"A thorough serious crime investigation works systematically through all the credible possibilities, and often in an investigation you will have more than one credible possibility.

"Therefore, just because we're doing a substantial phase of work in the forthcoming week doesn't mean that it's going to immediately lead to answers that will explain everything."

The Portuguese investigation into Madeleine's disappearance was wound up in 2008.

However, British police re-examined the evidence and opened its own investigation in July last year, closely followed by the Portuguese authorities.

The case has been kept in the public eye by a high-profile media campaign orchestrated by her parents Kate and Gerry McCann.

One line of inquiry for Scotland Yard is a lone male paedophile who staged a series of sex attacks on young British girls while they were on holiday in the Algarve.